Laser assisted topical anesthetic permeation

ABSTRACT

The present invention provides an improved method of administering a pharmaceutical composition, such as an anesthetic through the skin of a patient without the use of a sharp or needle. This method includes the step of irradiating the stratum corneum of a region of the skin of the patient using a laser. By a selection of parameters, the laser irradiates the surface of the skin precisely to a selectable depth, without causing clinically relevant damage to healthy proximal tissue. A pharmaceutical composition is then applied to the region of irradiation.

This application is a continuation-in-part of U.S. Ser. No. 08/792,335,filed Jan. 31, 1997, now abandoned, which is a continuation-in-part ofU.S. Ser. No. 08/126,241, filed Sep. 24, 1993, issued Jul. 1, 1997 asU.S. Pat. No. 5,643,252, all of which are incorporated herein byreference.

FIELD OF THE INVENTION

This invention is in the field of medical procedures, namely lasermedical equipment used in the delivery of anesthetics or pharmaceuticalsto, or the removal of fluids, gases or other biomolecules from, apatient.

BACKGROUND

The traditional method for the collection of small quantities of fluids,gases or other biomolecules from a patient utilizes mechanicalperforation of the skin with a sharp device such as a metal lancet orneedle. Additionally, the typical method of administering anesthetics orother pharmaceuticals is through the use of a needle.

These procedures have many drawbacks, including the possible infectionof health care workers and the public by the sharp device used toperforate the skin, as well as the cost of handling and disposal ofbiologically hazardous waste.

When skin is perforated with a sharp device such as a metal lancet orneedle, biological waste is created in the form of the “sharp”contaminated by the patient's blood and/or tissue. If the patient isinfected with blood-born agents, such as human immunodeficiency virus(HIV), hepatitis virus, or the etiological agent of any other diseases,the contaminated sharp poses a serious threat to others that might comein contact with it. For example, many medical workers have contractedHIV as a result of accidental contact with a contaminated sharp.

Post-use disposal of contaminated sharps imposes both logistical andfinancial burdens on the end user. These costs are imposed as a resultof the social consequences of improper disposal. For example, in the1980's improperly disposed biological wastes washed up on public beacheson numerous occasions. Improper disposal also permits others, such asintravenous drug users, to obtain contaminated needles and spreaddisease.

There exists an additional drawback of the traditional method of using aneedle for administering anesthetics or pharmaceuticals, as well as fordrawing fluids, gases or other biomolecules. The pain associated withbeing stabbed by a the sharp instrument can be a traumatizing procedure,especially in pediatric patients, causing significant stress and anxietyin the patient. Moreover, for drawing fluids, gases or otherbiomolecules, the stabbing procedure often must be repeated before asufficient sample is obtained.

The current technology for applying local anesthetic without the use ofneedles typically involves either (a) topical lidocaine mixtures, (b)iontophoresis, (c) carriers or vehicles which are compounds that modifythe chemical properties of either the stratum corneum, or thepharmaceutical, and (d) sonophoresis which involves modifying thebarrier function of stratum corneum by ultrasound. A cream containinglidocaine is commonly used, especially in pediatric patients, but needsto be applied for up to 60 minutes, and anesthesia is produced to adepth of only about 4 mm. The lack of lidocaine penetration is aconsequence of the barrier function of the stratum corneum. Inherentproblems with iontophoresis include the complexity of the deliverysystem, cost, and unknown toxicology of prolonged exposure to electricalcurrent. Additionally, the use of carriers or vehicles involvesadditional compounds which might modify the pharmacokinetics of thepharmaceutical of interest or are irratating.

Thus, a need exists for a technique to remove fluids, gases or otherbiomolecules or to administer anesthetics or other pharmaceuticals whichdoes not require a sharp instrument. The method and apparatus disclosedherein fulfill this need and obviate the need for the disposal ofcontaminated instruments, thereby reducing the risk of infection.

Lasers have been used in recent years as a very efficient precise toolin a variety of surgical procedures. Among potentially new sources oflaser radiation, the rare-earth elements are of major interest formedicine. One of the most promising of these is a YAG (yttrium,aluminum, garnet) crystal doped with erbium (Er) ions. With the use ofthis crystal, it is possible to build an erbium-YAG (Er:YAG) laser whichcan be configured to emit electromagnetic energy at a wavelength (2.94microns) which is strongly absorbed by, among other things, water. Whentissue, which consists mostly of water, is irradiated with radiation ator near this wavelength, energy is transferred to the tissue. If theintensity of the radiation is sufficient, rapid heating can resultfollowed by vaporization of tissue. In addition, deposition of thisenergy can result in photomechanical disruption of tissue. Some medicaluses of Er:YAG lasers have been described in the health-care disciplinesof dentistry, gynecology and ophthalmology. See, e.g., Bogdasarov, B.V., et al., “The Effect of Er:YAG Laser Radiation on Solid and SoftTissues,” Preprint 266, Institute of General Physics, Moscow, 1987;Bol'shakov, E. N. et al., “Experimental Grounds for Er:YAG LaserApplication to Dentistry,” SPIE 1353:160-169, Lasers and Medicine (1989)(these and all other references cited herein are expressly incorporatedby reference as if fully set forth in their entirety herein).

SUMMARY OF THE INVENTION

The present invention employs a laser to perforate or alter the skin ofa patient so as to remove fluids, gases or other biomolecules or toadminister anesthetics or other pharmaceuticals. Perforation oralteration is produced by irradiating the surface of the target tissuewith a pulse or pulses of electromagnetic energy from a laser. Prior totreatment, the care giver properly selects the wavelength, energyfluence (energy of the pulse divided by the area irradiated), pulsetemporal width and irradiation spot size so as to precisely perforate oralter the target tissue to a select depth and eliminate undesired damageto healthy proximal tissue.

According to one embodiment of the present invention, a laser emits apulsed laser beam, focused to a small spot for the purpose ofperforating or altering the target tissue. By adjusting the output ofthe laser, the laser operator can control the depth, width and length ofthe perforation or alteration as needed.

In another embodiment continuous-wave or diode lasers may be used toduplicate the effect of a pulsed laser beam. These lasers are modulatedby gating their output, or, in the case of a diode laser, by fluctuatingthe laser excitation current in a diode laser. The overall effect is toachieve brief irradiation, or a series of brief irradiations, thatproduce the same tissue permeating effect as a pulsed laser. The term“modulated laser” is used herein to indicate this duplication of apulsed laser beam.

The term, “perforation” is used herein to indicate the ablation of thestratum corneum to reduce or eliminate its barrier function. The term,“alteration” of the stratum corneum is used herein to indicate a changein the stratum corneum which reduces or eliminates the barrier functionof the stratum corneum and increases permeability without ablating, orby merely partially ablating, the stratum corneum itself. A pulse orpulses of infrared laser radiation at a subablative energy of, e.g., 60mJ (using a TRANSMEDICA® International, Inc. (“TRANSMEDICA™”) Er:YAGlaser with a beam of radiant energy with a wavelength of 2.94 microns, a200 μs (microsecond) pulse, and a 2 mm spot size) will alter the stratumcorneum. The technique may be used for transdermal drug delivery or forobtaining samples, fluids, gases or other biomolecules, from the body.Different wavelengths of laser radiation and energy levels less than orgreater than 60 mJ may also produce the enhanced permeability effectswithout ablating the skin.

The mechanism for this alteration of the stratum corneum is not certain.It may involve changes in lipid or protein nature or function or be dueto desiccation of the skin or mechanical alterations secondary topropagating pressure waves or cavitation bubbles. The pathway thattopically applied drugs take through the stratum corneum is generallythought to be through cells and/or around them, as well as through hairfollicles. The impermeability of skin to topically applied drugs isdependent on tight cell to cell junctions, as well as the biomolecularmakeup of the cell membranes and the intercellular milieu. Any changesto either the molecules that make up the cell membranes or intercellularmilieu, or changes to the mechanical structural integrity of the stratumcorneum and/or hair follicles can result in reduced barrier function. Itis believed that irradiation of the skin with radiant energy produced bythe Er:YAG laser causes measurable changes in the thermal properties, asevidenced by changes in the Differential Scanning Calorimeter (DSC)spectra as well as the Fourier Transform Infrared (FTIR) spectra ofstratum corneum. Changes in DSC and FTIR spectra occur as a consequenceof changes in molecules or macromolecular structure, or the environmentaround these molecules or structures. Without wishing to be bound to anyparticular theory, we can tentatively attribute these observations tochanges in lipids, water and protein molecules in the stratum corneumcaused by irradiation of molecules with electromagnetic radiation, bothby directly changing molecules as well as by the production of heat andpressure waves which can also change molecules.

Both perforation and alteration change the permeability parameters ofthe skin in a manner which allows for increased passage ofpharmaceuticals, as well as fluids, gases or other biomolecules, acrossthe stratum corneum.

Accordingly, one object of the present invention is to provide a meansfor perforating or altering the stratum corneum of a patient in a mannerthat does not result in bleeding. For example, the perforation oralteration created at the target tissue is accomplished by applying alaser beam that penetrates through the stratum corneum layer or both thestratum corneum layer and the epidermis, thereby reducing or eliminatingthe barrier function of the stratum corneum. This procedure allows theadministration of anesthetics or other pharmaceuticals, as well as theremoval of fluids, gases or other biomolecules, through the skin.Moreover, this procedure allows drugs to be administered continually onan outpatient basis over long periods of time. The speed and/orefficiency of drug delivery is thereby enhanced for drugs which wereeither slow or unable to penetrate skin.

A further object of this invention is to provide an alternative meansfor administering drugs that would otherwise be required to be takenthrough other means, such as orally or injected, thereby increasingpatient compliance and decreasing patient discomfort.

An additional object of this invention is to allow the taking ofmeasurements of various fluid constituents, such as glucose, or toconduct measurements of gases.

A further object of this invention is to avoid the use of sharps. Theabsence of a contaminated sharp will eliminate the risk of accidentalinjury and its attendant risks to health care workers, patients, andothers that may come into contact with the sharp. The absence of a sharpin turn obviates the need for disposal of biologically hazardous waste.Thus, the present invention provides an ecologically sound method foradministering anesthetics or other pharmaceuticals, as well as removingfluids, gases or other biomolecules.

In another embodiment a typical laser is modified to include a containerunit. Such a container unit can be added to: (1) increase the efficiencyin the collection of fluids, gases or other biomolecules; (2) reduce thenoise created when the laser beam perforates the patient's tissue; and(3) collect the ablated tissue. The optional container unit isalternatively evacuated to expedite the collection of the releasedmaterials such as the fluids, gases or other biomolecules. The containercan also be used to collect only ablated tissue. The noise created fromthe laser beam's interaction with the patient's skin may cause thepatient anxiety. The optional container unit reduces the noise intensityand therefore alleviates the patient's anxiety and stress. The containerunit also minimizes the risk of cross-contamination and guarantees thesterility of the collected sample. The placement of the container unitin the use of this invention is unique in that it covers the tissuebeing irradiated, at the time of irradiation by the laser beam, and istherefore able to collect the fluid, gas or other biomolecule samplesand/or ablated tissue as the perforation or alteration occurs. Thecontainer unit may also be modified for the purpose of containingmaterials, such as drugs, which may be applied before, simultaneously orshortly after irradiation.

A typical laser used for this invention requires no special skills touse. It can be small, lightweight and can be used with regular orrechargeable batteries. The greater the laser's portability and ease ofuse, the greater the utility of this invention in a variety of settings,such as a hospital room, clinic, or home.

Safety features can be incorporated into the laser that require that nospecial safety eyewear be worn by the operator of the laser, thepatient, or anyone else in the vicinity of the laser when it is beingused.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood and its advantagesappreciated by those skilled in the art by referring to the accompanyingdrawings wherein:

FIG. 1 shows a laser with its power source, high voltage pulse-formingnetwork, flashlamp, lasing rod, mirrors, housing and focusing lens.

FIG. 2 shows an optional spring-loaded interlock and optionally heatedapplicator.

FIG. 3 shows an alternative means of exciting a laser rod using a diodelaser.

FIG. 4 shows an alternative focusing mechanism.

FIGS. 5A & 5B show optional beam splatters for creating multiplesimultaneous perforations.

FIG. 6 shows a patch that can be used to sterilize the site ofirradiation.

FIGS. 7A & 7B show alternative patches for sterilization and/or deliveryof pharmaceuticals, and/or collection of fluids, gases or otherbiomolecules.

FIG. 8 shows an optional container unit for collecting fluids, gases orother biomolecules, ablated tissue, and/or other matter released fromthe site of irradiation, and for reducing noise resulting from theinteraction between the laser and the patient's tissue.

FIG. 9 shows a plug and plug perforation center.

FIG. 10 shows an optional container unit for collecting ablated tissueand reducing noise resulting from the interaction between the laser andthe patient's tissue.

FIG. 11 shows a roll-on device for the delivery of anesthetics orpharmaceuticals.

FIG. 12 shows an elastomeric mount for a solid state laser crystalelement with optional mirrored surfaces applied to each end of theelement.

FIG. 13 shows an example of a crystal rod with matte finish around thefull circumference of the entire rod.

FIG. 14 shows an example of a crystal rod with matte finish around thefull circumference of two-thirds of the rod.

FIG. 15 shows an example of a crystal rod with matte stripes along itslongitudinal axis.

FIG. 16 shows a cross-section of a crystal laser rod element surroundedby a material having an index of refraction greater than the index ofrefraction of the rod.

FIGS. 17A-17G show various examples of a container unit.

FIG. 18 shows an atomizer for the delivery of anesthetics orpharmaceuticals.

FIGS. 19a and 19 b shows examples of a container unit in use with alaser.

FIG. 20 shows an example of a lens with a mask.

FIG. 21 is a chart showing a study using corticosterone which showedenhanced permeation (over controls) at an energies of 77 mJ and 117 mJ.

FIG. 22 shows the decrease in the impedance of skin in vivo usingvarious laser pulse energies.

FIGS. 23-24 show in a permeation study of tritiated water (³H₂O)involving lased human skin at energies from 50 mJ (1.6 J/cm²) to 1250 mJ(40 J/cm²).

FIG. 25 shows histological sections of human skin irradiated at energiesof 50 mJ and 80 mJ.

FIG. 26 is a chart of a study using DNA showing enhanced permeationthrough skin irradiated at an energy of 150 mJ and 300 mJ.

FIG. 27 shows laser pulse energy (J) versus water loss through humanskin in vivo.

FIG. 28 is a chart showing a DSC scan of normally hydrated (66%) humanstratum corneum, and a scan of Er:YAG laser irradiated stratum corneumusing a subablative pulse energy of 60 mJ.

FIGS. 29-31 are charts showing the heat of transition (μJ), center ofthe transition (° C.) and the full-width at half-maximum of thetransition (° C.) of three peaks in the DSC spectra for stratum corneumtreated different ways.

FIGS. 32-33 are charts of FTIR spectra of control and lased stratumcorneum.

FIG. 34 shows Amide I band position (cm⁻⁴) as a function of stratumcorneum treatment.

FIG. 35 shows CH₂ vibration position (cm⁻⁴) as a function of stratumcorneum treatment.

FIG. 36 shows a histological section of rat skin that was irradiated at80 mJ.

FIG. 37 shows a histological section of human skin that was irradiatedat 80 mJ.

FIG. 38 shows in vivo blanching assay results.

FIGS. 39-41 shows permeation of γ-interferon, insulin and lidocaine,through human skin in vitro.

FIG. 42 shows an example of a beam splitter suitable for makingsimultaneous irradiation sites.

FIG. 43 shows one possible pattern of perforation or alteration sitesusing a beam splitter.

DETAILED DESCRIPTION

This invention provides a method for perforating or altering skin foreither the sampling of fluids, gases or other biomolecules or theadministration of anesthetics or other pharmaceuticals. The inventionutilizes a laser beam, specifically focused, and lasing at anappropriate wavelength, to create small perforations or alterations inthe skin of a patient. In a preferred embodiment, the laser beam has awavelength between about 0.2 and 10 microns. More preferably, thewavelength is between about 1.5 and 3.0 microns. Most preferably thewavelength is about 2.94 microns. In one embodiment, the laser beam isfocused with a lens to produce an irradiated spot on the skin with asize of approximately 0.5 microns −5.0 cm diameter. Optionally, the spotcan be slit-shaped, with a width of about 0.05-0.5 mm and a length of upto 2.5 mm.

The caregiver may consider several factors in defining the laser beam,including wavelength, energy fluence, pulse temporal width andirradiation spot-size. In a preferred embodiment, the energy fluence isin the range of 0.03-100,000 J/cm². More preferably, the energy fluenceis in the range of 0.03-9.6 J/cm². The beam wavelength is dependent inpart on the laser material, such as Er:YAG. The pulse temporal width isa consequence of the pulse width produced by, for example, a bank ofcapacitors, the flashlamp, and the laser rod material. The pulse widthis optimally between 1 fs (femtosecond) and 1,000 μs.

According to the method of the present invention the perforation oralteration produced by the laser need not be produced with a singlepulse from the laser. In a preferred embodiment the caregiver produces aperforation or alteration through the stratum corneum by using multiplelaser pulses, each of which perforates or alters only a fraction of thetarget tissue thickness.

To this end, one can roughly estimate the energy required to perforateor alter the stratum corneum with multiple pulses by taking the energyin a single pulse, and dividing by the number of pulses desirable. Forexample, if a spot of a particular size requires 1 J of energy toproduce a perforation or alteration through the entire stratum corneum,then one can produce a qualitatively similar perforation or alterationusing ten pulses, each having {fraction (1/10)}th the energy. Because itis desirable that the patient not move the target tissue during theirradiation (human reaction times are on the order of 100 ms or so), andthat the heat produced during each pulse not significantly diffuse, in apreferred embodiment the pulse repetition rate from the laser should besuch that complete perforation is produced in a time of less than 100ms. Alternatively, the orientation of the target tissue and the lasercan be mechanically fixed so that changes in the target location do notoccur during the longer irradiation time.

To penetrate the skin in a manner which does not induce much if anyblood flow, skin is perforated or altered through the outer surface,such as the stratum corneum layer, but not as deep as the capillarylayer. The laser beam is focussed precisely on the skin, creating a beamdiameter at the skin in the range of 0.5 microns −5.0 cm. The width canbe of any size, being controlled by the anatomy of the area irradiatedand the desired permeation rate of the pharmaceutical to be applied, orfluid, gas or other biomolecule to be removed. The focal length of thefocussing lens can be of any length, but in one embodiment it is 30 mm.

By modifying wavelength, pulse length, energy fluence (which is afunction of the laser energy output (in Joules) and size of the beam atthe focal point (cm²)), and irradiation spot size, it is possible tovary the effect on the stratum corneum between ablation (perforation)and non-ablation or partial ablation (alteration). Both ablation andnon-ablative alternation of the stratum corneum result in enhancedpermeation of subsequently applied pharmaceuticals, or removal of fluid,gas or other biomolecule.

For example, by reducing the pulse energy while holding other variablesconstant, it is possible to change between ablative and non-ablativetissue-effect. Using the TRANSMEDICA™ Er:YAG laser, which has a pulselength of about 300 μs, with a single pulse or radiant energy andirradiating a 2 mm spot on the skin, a pulse energy above approximately100 mJ causes partial or complete ablation, while any pulse energy belowapproximately 100 mJ causes partial ablation or non-ablative alterationto the stratum corneum. Optionally, by using multiple pulses, thethreshold pulse energy required to enhance pharmaceutical delivery isreduced by a factor approximately equal to the number of pulses.

Alternatively, by reducing the spot size while holding other variablesconstant, it is also possible to change between ablative andnon-ablative tissue-effect. For example, halving the spot area willresult in halving the energy required to produce the same effect.Irradiations down to 0.5 microns can be obtained, for example, bycoupling the radiant output of the laser into the objective lens of amicroscope objective (e.g. as available from Nikon, Inc., Melville,N.Y.). In such a case, it is possible to focus the beam down to spots onthe order of the limit of resolution of the microscope, which is perhapson the order of about 0.5 microns. In fact, if the beam profile isGaussian, the size of the affected irradiated area can be less than themeasured beam size and can exceed the imaging resolution of themicroscope. To non-ablatively alter tissue in this case, it would besuitable to use a 3.2 J/cm² energy fluence, which for a half-micron spotsize, would require a pulse energy of about 5 nJ. This low a pulseenergy is readily available from diode lasers, and can also be obtainedfrom, for example, the Er:YAG laser by attenuating the beam with anabsorbing filter, such as glass.

Optionally, by changing the wavelength of radiant energy while holdingthe other variables constant, it is possible to change between anablative and non-ablative tissue-effect. For example, using Ho:YAG(holmium:YAG; 2.127 microns) in place of the Er:YAG (erbium:YAG; 2.94microns) laser, would result in less absorption of energy by the tissue,creating less of a perforation or alteration.

Picosecond and femtosecond pulses produced by lasers can also be used toproduce alteration or ablation in skin. This can be accomplished withmodulated diode or related microchip lasers, which deliver single pulseswith temporal widths in the 1 femtosecond to 1 ms range. (See D. Sternet al., “Corneal Ablation by Nanosecond, Picosecond, and FemtosecondLasers at 532 and 625 nm,” Corneal Laser Ablation, vol. 107, pp. 587-592(1989), incorporated herein by reference, which discloses the use ofpulse lengths down to 1 femtosecond).

According to one embodiment of the present invention, the anesthetic orpharmaceutical can be administered immediately after laser irradiation.Two embodiments of this invention incorporate an atomizer (FIG. 18) or aroll-on device (FIG. 11). In the case of a roll-on device, the laserbeam propagates through hole 162 incorporated in ball 164 of the roll-ondevice. In the alternative, the roll-on device can be positionedadjacent to the path of the laser beam through the disposableapplicator. After irradiation, the roll-on device is rolled over theirradiated site, thereby administering the desired anesthetic orpharmaceutical. In the case of an atomizer, the anesthetic isadministered from a drug reservoir 166 through the use of compressedgas. After irradiation, a cylinder 168 containing compressed gas (suchas, for example, carbon dioxide) is triggered to spray a set amount ofanesthetic or pharmaceutical over the irradiated site.

Alternatively, it would be beneficial to apply positive pressure to adrug reservoir thereby pushing the drug into the skin, or negativepressure in a collection reservoir thus enhancing the diffusion ofanalytes out of the skin. Ambient atmospheric pressure is 760 mm Hg, or1 atmosphere. Because of hydrostatic pressure in a standing individual,the relative pressure difference in the head may be 10 mm Hg below areference value taken at the level of the neck, and 90 mm Hg higher inthe feet. The arms may be between 8 and 35 mm Hg. Note also that becauseof the beating heart, a dynamic pressure (in a normal, healthyindividual) of between 80-120 mm Hg is in the circulation. Thus, topermeate a drug through the skin (say in the arm), a positive pressureof greater than about (760 mm+35 mm) Hg would be suitable. A pressurejust slightly over 1 atmosphere would be suitable to enhance drugpermeation, and yet would not enhance diffusion into the blood streambecause of the dynamic pressures in the blood stream. A higher pressuremight beneficially enhance diffusion into the blood stream. However,pressures much greater than perhaps 5 or so atmospheres for extendedtimes might actually produce side effects.

In another embodiment of the present invention, an ink jet or mark isused for marking the site of irradiation. The irradiated sites are oftennot easily visible to the eye, consequently the health care provider maynot know exactly where to apply the anesthetic or pharmaceuticalsubsequent to laser irradiation. This invention further providestechniques to mark the skin so that the irradiation site is apparent.For example, an ink-jet (analogous to those used in ink-jet printers)can be engaged prior to, during or immediately after laser irradiation.Additionally, a circle can be marked around the ablation site, or aseries of lines all pointing inward to the ablation site can be used.Alternatively, the disposable safety-tip/applicator can be marked on theend (the end that touches up against the skin of the patient) with apigment. Engaging the skin against the applicator prior to, during, orimmediately after lasing results in a mark on the skin at the site ofirradiation.

For certain purposes, it is useful to create multiple perforations oralterations of the skin simultaneously or in rapid sequence. Toaccomplish this, a beam splitter can optionally be added to the laser,or a rapidly pulsing laser, such as a diode or related microchip lasers,may be used. Multiple irradiated sites, created simultaneously orsequentially, would result in an increased uptake of drugs as comparedto a single irradiation site (i.e. an increase in uptake proportional tothe total number of ablated sites). An example of a beam splitter 48suitable for making simultaneous irradiation sites for use with a lasercan be found in FIG. 42. Any geometric pattern of spots can be producedon the skin using this technique. Because the diffusion into skin oftopically applied drugs can be approximated as symmetric, a beneficialpattern of irradiation spots for local drug delivery (such that auniform local concentration would result over as wide an area aspossible) would be to position each spot equidistant from each other ina staggered matrix pattern (FIG. 43).

Alternatively, multiple irradiation sites, or an irradiated area ofarbitrary size and shape, could be produced with use of a scanner. Forexample, oscillating mirrors which reflect the beam of laser radiantenergy can operate as a scanner.

For application of the laser device for anesthetic or pharmaceuticaldelivery, as well as fluid, gas or other biomolecule removal, the laseris manipulated in such a way that a portion of the patient's skin ispositioned at the site of the laser focus within the applicator. Forperforations or alterations for the delivery of anesthetics and otherpharmaceuticals, as well as fluid, gas or other biomolecule removal, aregion of the skin which has less contact with hard objects or withsources of contamination is preferred, but not required. Examples areskin on the arm, leg, abdomen or back. Optionally, the skin heatingelement is activated at this time in order to reduce the laser energyrequired for altering or ablating the stratum corneum.

Preferably a holder is provided with a hole coincident with the focalplane of the optical system. Optionally, as shown in FIG. 2, aspring-loaded interlock 36 can be attached to the holder, so that whenthe patient applies a small amount of pressure to the interlock, torecess it to the focal point, a switch is closed and the laser willinitiate a pulse of radiation. In this setup, the focal point of thebeam is not in line with the end of the holder until that end isdepressed. In the extremely unlikely event of an accidental discharge ofthe laser before proper positioning of the tissue at the end of thelaser applicator, the optical arrangement will result in an energyfluence rate that is significantly low, thus causing a negligible effecton unintentional targets.

The method of this invention may be enhanced by using a laser of awavelength that is specifically absorbed by the skin components ofinterest (e.g., water, lipids or protein) which strongly affect thepermeation of the skin tissues. However, choosing a laser that emits astrongly absorbed wavelength is not required. Altering the lipids instratum corneum may allow enhanced permeation while avoiding the higherenergies that are necessary to affect the proteins and water.

It would be beneficial to be able to use particular lasers other thanthe Er:YAG for stratum corneum ablation or alteration. For example,laser diodes emitting radiant energy with a wavelength of 810 nm (0.8microns) are inexpensive, but such wavelength radiation is only poorlyabsorbed by tissue. In a further embodiment of this invention, a dye isadministered to the skin surface, either by application over intactstratum corneum, or by application over an Er:YAG laser treated site (sothe that deep dye penetration can occur), that absorbs such a wavelengthof radiation. For example, indocyanine green (ICG), which is a harmlessdye used in retina angiography and liver clearance studies, absorbsmaximally at 810 nm when in plasma (Stephen Flock and Steven Jacques,“Thermal Damage of Blood Vessels in a Rat Skin-Flap Window Chamber UsingIndocyanine Green and a Pulsed Alexandrite Laser: A Feasibility Study,”Laser Med. Sci. 8, 185-196, 1993). This dye, when in stratum corneum, isexpected to absorb the 810 nm radiant energy from a diode laser (e.g. aGaAlAs laser) thereby raising the temperature of the tissue, andsubsequently leading to ablation or molecular changes resulting inreduced barrier function.

Alternatively, it is possible to chemically alter the optical propertiesof the skin to enhance subsequent laser radiant energy absorptionwithout chemicals actually being present at the time of laserirradiation. For example, 5-aminolevulinic acid (5-ALA) is a precursorto porphyrins, which are molecules involved in hemoglobin production andbehavior. Porphyrins are strong absorbers of light. Administration of5-ALA stimulates production of porphyrins in cells, but is itselfconsumed in the process. Subsequently, there will be enhanced absorptionof radiant energy in this tissue at wavelengths where porphyrins absorb(e.g., 400 nm or 630 nm).

Another way to enhance the absorption of radiant energy in stratumcorneum without the addition of an exogenous absorbing compound is tohydrate the stratum corneum by, for example, applying an occlusivebarrier to the skin prior to laser irradiation. In this situation, thewater produced within the body itself continues to diffuse through thestratum corneum and propagate out through pores in the skin, but isprevented from evaporating by the occlusive barrier. Thus, the moistureis available to further saturate the stratum corneum. As the radiantenergy emitted by the Er:YAG laser is strongly absorbed by water, thisprocess would increase the absorption coefficient of the stratumcorneum, and so less energy would be required to induce the alterationsor ablations in the stratum corneum necessary for enhanced topical drugdelivery.

Additionally, the laser ablated site eventually heals as a result ofinfiltration of keratinocytes and keratin (which takes perhaps two weeksto complete), or by the diffusion of serum up through the ablated siteswhich form a clot (or eschar) which effectively seals the ablated site.For long term topical delivery of drugs, or for multiple sequentialadministrations of topical drugs, it would be beneficial to keep theablated site open for an extended length of time.

Thus, in an additional embodiment of this invention, the ablated ornon-ablated site is kept open by keeping the area of irradiation moist.This is accomplished by minimizing contact of air with the ablated siteand/or providing fluid to keep the ablated site moist and/orbiochemically similar to stratum corneum. The application of a patch(containing, for example, an ointment such as petroleum jelly or anointment containing hydrocortisone) over the site would help to keep itopen. A hydrogel patch would also serve to provide the necessarymoisture. Additionally, cytotoxic drugs such as cisplatin, bleomycin,doxurubicin, and methotrexate, for example, topically applied in lowconcentrations would locally prevent cellular infiltration and woundrepair. Furthermore, application of vitamin C (ascorbic acid), or otherknown inhibitors of melanin production, following irradiation, wouldhelp to prevent additional skin coloration in the area followingtreatment.

Continuous-Wave (CW) Laser Scanning

It is possible, under machine and microprocessor control, to scan alaser beam (either continuous-wave or pulsed) over the target tissue,and to minimize or eliminate thermal damage to the epidermis or adjacentanatomical structures.

For example, a scanner (made up of electro-optical or mechanicalcomponents) can be fashioned to continually move the laser beam over auser-defined area. This area can be of arbitrary size and shape. Thepath for the scan could be spiral or raster. If the laser is pulsed, ormodulated, then it would be possible to do a discrete random patternwhere the scanning optics/mechanics directs the beam to a site on theskin, the laser lases, and then the scanning optics/mechanics directsthe beam to a different site (preferable not adjacent to the first spotso that the skin has time to cool before an adjacent spot is heated up).

This scanning technique has been used before with copper-vapor lasers(in treating port-wine stains) and is in use with CO₂ lasers for thepurpose of facial resurfacing. In the case of the former, thesubepidermal blood vessels are targeted, while in the latter, about 100microns of tissue is vaporized and melted with each laser pass.

Delivery of Anesthesia

A laser can be used to perforate or alter the skin through the outersurface, such as the stratum corneum layer, but not as deep as thecapillary layer, to allow localized anesthetics to be topicallyadministered. Topically applied anesthetics must penetrate the stratumcorneum layer in order to be effective. Presently, compounds acting asdrug carriers are used to facilitate the transdermal diffusion of somedrugs. These carriers sometimes change the behavior of the drug, or arethemselves toxic.

With the other parameters set, the magnitude of the laser pump sourcewill determine the intensity of the laser pulse, which will in turndetermine the depth of the resultant perforation or alteration.Therefore, various settings on the laser can be adjusted to allowperforation or alteration of different thicknesses of stratum corneum.

Optionally, a beam-dump can be positioned in such a way as not to impedethe use of the laser for perforation or alteration of extremities. Thebeam-dump will absorb any stray electromagnetic radiation from the beamwhich is not absorbed by the tissue, thus preventing any scattered raysfrom causing damage. The beam-dump can be designed so as to be easilyremoved for situations when the presence of the beam-dump would impedethe placement of a body part on the applicator.

This method of delivering anesthetic creates a very small zone in whichtissue is irradiated, and only an extremely small zone of thermalnecrosis. A practical round irradiation site can range from 0.1-5.0 cmin diameter, while a slit shaped hole can range from approximately0.05-0.5 mm in width and up to approximately 2.5 mm in length, althoughother slit sizes and lengths can be used. As a result, healing isquicker or as quick as the healing after a skin puncture with a sharpimplement. After irradiation, anesthetic can then be applied directly tothe skin or in a pharmaceutically acceptable formulation such as acream, ointment, lotion or patch.

Alternatively, the delivery zone can be enlarged by strategic locationof the irradiation sites and by the use of multiple sites. For example,a region of the skin may be anesthetized by first scanning the desiredarea with a pulsing laser such that each pulse is sufficient to causeperforation or alteration. This can be accomplished with modulated diodeor related microchip lasers, which deliver single pulses with temporalwidths in the 1 femtosecond to 1 ms range. (See D. Stem et al., “CornealAblation by Nanosecond, Picosecond, and Femtosecond Lasers at 532 and625 nm, ” Corneal Laser Ablation, vol. 107, pp. 587-592 (1989),incorporated herein by reference, which discloses the use of pulselengths down to 1 femtosecond). Anesthetic (e.g., 10% lidocaine) wouldthen be applied over the treated area to achieve a zone of anesthesia.

The present method can be used for transport of a variety ofanesthetics. These anesthetics are different in their system and localtoxicity, degree of anesthesia produced, time to onset of anesthesia,length of time that anesthesia prevails, biodistribution, and sideeffects. Examples of local anesthetic in facial skin-resurfacing with alaser can be found in Fitzpatrick R. E., Williams B. Goldman M. P.,“Preoperative Anesthesia and Postoperative Considerations in LaserResurfacing,” Semin. Cutan. Med. Surg. 15(3):170-6, 1996. A partial listconsists of: cocaine, procaine, mepivacaine, etidocaine, ropivacaine,bupivacaine, lidocaine, tetracain, dibucaine, prilocaine,chloroprocaine, hexlcaine, fentanyl, procainamide, piperocaine, MEGX(des-ethyl lidocaine) and PPX (pipecolyl xylidine). A reference on localanesthetic issues can be found in Rudolph de Jong, “Local Anesthetics,”Mosby-Year Book: St Louis, 1994.

Delivery of Pharmaceuticals

The present method can also be used to deliver pharmaceuticals in amanner similar to the above described delivery of anesthesia. Byappropriate modification of the power level, and/or the spot size of thelaser beam, perforations or alterations can be made which do notpenetrate as deep as the capillary layer. These perforations oralterations can be made through only the outer surfaces, such as thestratum corneum layer or both the stratum corneum layer and theepidermis. Optionally an optical beam-splitter or multiply pulsed lasercan be employed so that either single or multiple perforations oralterations within a desired area can be made. After perforation oralteration, the pharmaceutical can be applied directly to the skin or ina pharmaceutically acceptable formulation such as a cream, ointment,lotion or patch.

The present method can be used for transport of a variety ofsystemically acting pharmaceutical substances. For example nitroglycerinand antinauseants such as scopolamine; antibiotics such as tetracycline,streptomycin, sulfa drugs, kanamycin, neomycin, penicillin, andchloramphenicol; various hormones, such as parathyroid hormone, growthhormone, gonadotropins, insulin, ACTH, somatostatin, prolactin,placental lactogen, melanocyte stimulating hormone, thyrotropin,parathyroid hormone, calcitonin, enkephalin, and angiotensin; steroid ornon-steroid anti-inflammatory agents, and systemic antibiotic, antiviralor antifungal agents.

Delivery of Locally Acting Pharmaceuticals

Laser-assisted perforation or alteration provides a unique site forlocal uptake of pharmaceutical substances to a desired region. Thus,high local concentrations of a substance may be achieved which areeffective in a region proximal to the irradiated site by virtue oflimited dilution near the site of application. This embodiment of thepresent invention provides a means for treating local pain orinfections, or for application of a substance to a small specified area,directly, thus eliminating the need to provide high, potentially toxicamounts systemically through oral or i.v. administration. Locally actingpharmaceuticals such as alprostadil (for example Caverject fromPharmacia & Upjohn), various antibiotics, antiviral or antifungalagents, or chemotherapy or anti-cancer agents, can be delivered usingthis method to treat regions proximal to the delivery site. Protein orDNA based biopharmaceutical agents can also be delivered using thismethod.

Immunization

As for delivery of pharmaceuticals, antigens derived from a virus,bacteria or other agent which stimulates an immune response can beadministered through the skin for immunization purposes. Theperforations or alterations are made through the outer layers of theskin, either singly or multiply, and the immunogen is provided in anappropriate formulation. For booster immunizations, where delivery overa period of time increases the immune response, the immunogen can beprovided in a formulation which penetrates slowly through theperforations or alterations, but at a rate faster than possible throughunperforated or unaltered skin.

This approach offers clinicians a new approach for immunizations bysolving some of the problems encountered with other routes ofadministration (e.g. many vaccine preparations are not efficaciousthrough oral or intravenous routes). Further, the skin is often thefirst line of defense for invading microbes and the immune response inthe skin is partially composed of Immunoglobulin A (IgA) antibodies likethat of the mucous membranes. Scientists have long sought ways to inducemucosal immunity using various vaccine preparations. Unfortunately theyhave been met with limited success because in order to generate an IgAresponse, vaccine preparations must be delivered to mucous membranes inthe gut or sinuses which are difficult to reach with standardformulations. By immunizing intradermally, unique populations ofantibodies may be generated which include IgA, a critical element ofmucosal immunity. This laser-assisted intradermal method of antigenpresentation thereby may be used as a means to generate IgA antibodiesagainst invading organisms.

Delivery of Allergens

Traditional allergy testing requires the allergist to make multiplepricks on the patient's skin and apply specific allergens to make adetermination regarding intradermal hypersensitivity. The method of thisinvention can be used to deliver allergens reproducibly for allergytesting. Multiple perforations or alterations can be made through theouter layer of the skin without penetrating to the capillary level. Avariety of allergens can then be applied to the skin, as in a skin patchtest. One of the benefits of this methodology is that the stratumcorneum barrier function compromise (i.e. laser irradiation) is moreconsistent than pricks made with a sharp.

Delivery of Permeation Enhancers

Certain compounds may be used to enhance the permeation of substancesinto the tissues below perforated or ablated stratum corneum. Suchenhancers include DMSO, alcohols and salts. Other compounds specificallyaid permeation based on specific effects such as by increasing ablationor improving capillary flow by limiting inflammation (i.e. salicylicacid). The method of this invention can be used to deliver thesepermeation enhancers. Multiple or single perforations or alterations canbe made through the outer layer of the skin without penetrating to thecapillary level. Subsequently, a variety of permeation enhancers can beapplied to the irradiated site, as in a skin patch.

Delivery of Anti-Inflammatory Drugs

Analgesics and other non-steroid anti-inflammatory agents, as well assteroid anti-inflammatory agents may be caused to permeate throughperforated or altered stratum corneum to locally affect tissue withinproximity of the irradiated site. For example, anti-inflammatory agentssuch as Indocin (Merck & Co.), a non-steroidal drug, are effectiveagents for treatment of rheumatoid arthritis when taken orally, yetsometimes debilitating gastrointestinal effects can occur. Byadministering such agents through laser-assisted perforation oralteration sites, these potentially dangerous gastrointestinalcomplications may be avoided. Further, high local concentrations of theagents may be achieved more readily near the site of irradiation asopposed to the systemic concentrations achieved when orallyadministered.

Drawing Fluids, Gases or other Biomolecules

A laser can be used to perforate or alter the skin through the outersurface, such as the stratum corneum layer, but not as deep as thecapillary layer, to allow the collection of fluids, gases or otherbiomolecules. The fluid, gas or other biomolecule can be used for a widevariety of tests. With the other parameters set, the magnitude of thelaser pump source will determine the intensity of the laser pulse, whichwill in turn determine the depth of the resultant perforation oralteration. Therefore, various settings on the laser can be adjusted toallow penetration of different thicknesses of skin.

Optionally, a beam-dump can be positioned in such a way as not to impedethe use of the laser for perforation or alteration of extremities. Thebeam-dump will absorb any stray electromagnetic radiation from the beamthat is not absorbed by the tissue, thus preventing any scattered raysfrom causing damage. The beam-dump can be designed to be easily removedfor situations when the presence of the beam-dump would impede theplacement of a body part on the applicator.

This method of drawing fluids, gases or other biomolecules creates avery small zone in which tissue is irradiated, and only an extremelysmall zone of thermal necrosis. For example, a practical round hole canrange from about 0.1-1 mm in diameter, while a slit shaped hole canrange from about approximately 0.05-0.5 mm in width and up toapproximately 2.5 mm in length. As a result, healing is quicker or asquick as the healing after a skin puncture with a sharp implement.

The fluid, gas or other biomolecule can be collected into a suitablevessel, such as a small test tube or a capillary tube, or in a containerunit placed between the laser and the tissue as described above. Theprocess does not require contact. Therefore, neither the patient, thefluid, gas or other biomolecule to be drawn, or the instrument creatingthe perforation or alteration is contaminated.

The technique of the present invention may be used to sampleextracellular fluid in order to quantify glucose or the like. Glucose ispresent in the extracellular fluid in the same concentration as (or in aknown proportion to) the glucose level in blood (e.g. Lonnroth P.Strindberg L. Validation of the “internal reference technique” forcalibrating micro dialysis catheters in situ, Acta PhysiologicalScandinavica, 153(4):37580, 1995 Apr.).

The perforation or alteration of the stratum corneum causes a localincrease in the water loss through the skin (referred to astransepidermal water loss, or TEWL). As shown in FIG. 27, withincreasing laser energy fluence (J/cm²), there is a correspondingincrease in water loss. The tape strip data is a positive control thatproves that the measurement is indeed sensitive to increased skin waterevaporation.

Two of the energies used in FIG. 27, 40 mJ and 80 mJ (1.27 and 2.55J/cm²) are non-ablative and therefore show that non-ablative energiesallow the alteration of the barrier function of stratum corneum, therebyresulting in enhanced transepidermal water loss which can provide adiagnostic sample of extracellular fluid.

Besides glucose, other compounds and pathological agents also can beassayed in extracellular fluid. For example, HIV is presentextracellularly and may be assayed according to the present method. Thebenefit to obtaining samples for HIV analysis without having to drawblood with a sharp that can subsequently contaminate the health-careprovider is obvious. Additionally, the present invention can be used toemploy lasers non-ablatively to reduce or eliminate the barrierproperties of non-skin barriers in the human body, such as theblood-brain interface membranes, such as that positioned between thebrain's third ventricle and the hypothalamus, the sclera of the eye orany mucosal tissue, such as in the oral cavity.

Alteration without Ablation

There are advantages to the technique of altering and not ablating thestratum corneum. In a preferred embodiment, the skin is altered, notablated, so that its structural and biochemical makeup allow drugs topermeate. The consequence of this embodiment is: (1) the skin afterirradiation still presents a barrier, albeit reduced, to externalfactors such as viruses and chemical toxins; (2) less energy is requiredthan is required to ablate the stratum corneum, thus smaller and cheaperlasers can be used; and (3) less tissue damage occurs, thus resulting inmore rapid and efficient healing.

Radiant Energy vs Laser Radiant Energy

The radiant energy emitted by lasers has the properties of beingcoherent, monochromatic, collimated and (typically) intense.Nevertheless, to enhance transdermal drug delivery or fluid, gas orbiomolecule collection, the radiant energy used need not have theseproperties, or alternatively, can have one of all of these properties,but can be produced by a non-laser source.

For example, the pulsed light output of a pulsed xenon flashlamp can befiltered with an optical filter or other wavelength selection device,and a particular range of wavelengths can be selected out of the radiantenergy output. While the incoherent and quasi-monochromatic output ofsuch a configuration cannot be focussed down to a small spot as cancoherent radiant energy, for the aforementioned purpose that may not beimportant as it could be focused down to a spot with a diameter on theorder of millimeters. Such light sources can be used in a continuouswave mode if desirable.

The infrared output of incandescent lights is significantly more thantheir output in the visible, and so such light sources, if suitablyfiltered to eliminate undesirable energy that does not reduce barrierfunction, could be used for this purpose. In another embodiment of theinvention, it would be possible to use an intense incandescent light(such as a halogen lamp), filter it with an optical filter or similardevice, and used the continuous-wave radiant energy output to decreasethe barrier function of stratum corneum without causing ablation. All ofthese sources of radiant energy can be used to produce pulses, orcontinuos-wave radiant energy.

Laser Device

The practice of the present invention has been found to be effectivelyperformed by various types of lasers; for example, the TRANSMEDICA™Er:YAG laser perforator, or the Schwartz Electro-Optical Er:YAG laser.Preferably, any pulsed laser producing energy that is strongly absorbedin tissue may be used in the practice of the present invention toproduce the same result at a nonablative wavelength, pulse length, pulseenergy, pulse number, and pulse rate. However, lasers which produceenergy that is not strongly absorbed by tissue may also be used, albeitless effectively, in the practice of this invention. Additionally, asdescribed herein, continuous-wave lasers may also be used in thepractice of this invention.

FIGS. 1 and 2 are diagrammatic representations a typical laser that canbe used for this invention. As shown in FIGS. 1 and 2, a typical lasercomprises a power connection which can be either a standard electricalsupply 10, or optionally a rechargeable battery pack 12, optionally witha power interlock switch 14 for safety purposes; a high voltagepulse-forming network 16; a laser pump-cavity 18 containing a laser rod20, preferably Er:YAG; a means for exciting the laser rod, preferably aflashlamp 22 supported within the laser pump-cavity; an opticalresonator comprised of a high reflectance mirror 24 positioned posteriorto the laser rod and an output coupling mirror 26 positioned anterior tothe laser rod; a transmitting focusing lens 28 positioned beyond theoutput coupling mirror; optionally a second focusing cylindrical lens 27positioned between the output coupling mirror and the transmittingfocusing lens; an applicator 30 for positioning the subject skin at thefocal point of the laser beam, which is optionally heated for examplewith a thermoelectric heater 32, attached to the laser housing 34; aninterlock 36 positioned between the applicator and the power supply; andoptionally a beam dump 38 attached to the applicator with a fingertipaccess port 40.

The laser typically draws power from a standard 110 V or 220 V AC powersupply 10 (single phase, 50 or 60 Hz) which is rectified and used tocharge up a bank of capacitors included in the high voltagepulse-forming network 16. Optionally, a rechargeable battery pack 12 canbe used instead. The bank of capacitors establishes a high DC voltageacross a high output flashlamp 22. Optionally a power interlock 14, suchas a keyswitch, can be provided which will prevent accidental chargingof the capacitors and thus accidental laser excitation. A furtherinterlock can be added to the laser at the applicator, such as aspring-loaded interlock 36, so that discharge of the capacitors requiresboth interlocks to be enabled.

With the depression of a switch, a voltage pulse can be superimposed onthe already existing voltage across the flashlamp in order to cause theflashlamp to conduct, and, as a consequence, initiate the flash. Thelight energy from the flashlamp is located in the laser cavity 18 thathas a shape such that most of the light energy is efficiently directedto the laser rod 20, which absorbs the light energy, and, uponde-excitation, subsequently lases. The laser cavity mirrors of low 26and high 24 reflectivity, positioned collinearly with the long-axis ofthe laser rod, serve to amplify and align the laser beam.

Optionally, as shown in FIG. 12 the laser cavity mirrors comprisecoatings 124, 126, applied to ends of the crystal element and which havethe desired reflectivity characteristics. In a preferred embodiment anEr:YAG crystal is grown in a boule two inches in diameter and fiveinches long. The boule is core drilled to produce a rod 5-6 millimetersin diameter and five inches long. The ends of the crystal are ground andpolished. The output end, that is the end of the element from which thelaser beam exits, is perpendicular to the center axis of the rod within5 arc minutes. The flatness of the output end is {fraction (1/10)} awavelength (2.9 microns) over 90% of the aperture. The high reflectanceend, that is the end opposite the output end, comprises a two meterconvex spherical radius. The polished ends are polished so that thereare an average of ten scratches and five digs per Military SpecificationMil-0-13830A. Scratch and dig are subjective measurements that measurethe visibility of large surface defects such as defined by U.S. militarystandards. Ratings consist of two numbers, the first being thevisibility of scratches and the latter being the count of digs (smallpits). A #10 scratch appears identical to a 10 micron wide standardscratch while a #1 dig appears identical to a 0.01 mm diameter standardpit. For collimated laser beams, one normally would use optics withbetter than a 40-20 scratch-dig rating.

Many coatings are available from Rocky Mountain Instruments, ColoradoSprings, Colo. The coating is then vacuum deposited on the ends. For a2.9 micron wavelength the coatings for the rear mirrored surface 124should have a reflectivity of greater than 99%. The coating for theoutput end surface, by contrast, should have a reflectance of between93% and 95%, but other mirrored surfaces with reflectivity as low as 80%are useful. Other vacuum deposited metallic coatings with knownreflectance characteristics are widely available for use with otherlaser wavelengths.

The general equation which defines the reflectivity of the mirrors in alaser cavity necessary for the threshold for population inversion is:

R ₁ R ₂(1−a _(L))² exp[(g ₂₁−α)2L]=1

where the R₁ and R₂ are the mirrors' reflectivities, a_(L) is the totalscattering losses per pass through the cavity, g₂₁ is the gaincoefficient which is the ratio of the stimulated emission cross sectionand population inversion density, α is the absorption of the radiationover one length of the laser cavity, and L is the length of the lasercavity. Using the above equation, one can select a coating with theappropriate spectral reflectivity from the following references. W.Driscoll and W. Vaughan, “Handbook of Optics,” ch. 8, eds., McGraw-Hill:NY (1978); M. Bass, et al., “Handbook of Optics,” ch. 35, eds., McGrawHill: NY (1995).

Optionally, as also shown in FIG. 12, the crystal element may benon-rigidly mounted. In FIG. 12 an elastomeric material O-ring 128 is ina slot in the laser head assembly housing 120 located at the highreflectance end of the crystal element. A second elastomeric materialO-ring 130 is in a second slot in the laser head assembly at the outputend of the crystal element. The O-rings contact the crystal element byconcentrically receiving the element as shown. However, elastomericmaterial of any shape may be used so long as it provides elastomericsupport for the element (directly or indirectly) and thereby permitsthermal expansion of the element. Optionally, the flash lamp 22 may alsobe non-rigidly mounted. FIG. 12 shows elastomeric O-rings 134, 136, eachin its own slot within the laser head assembly housing. In FIG. 12 theO-rings 134 and 136 concentrically receive the flash lamp. However, theflash lamp may be supported by elastomeric material of other shapes,including shapes without openings.

Optionally, as shown in FIG. 3, a diode laser 42 which produces apump-beam collinear with the long-axis of the laser crystal can be usedinstead of the flashlamp to excite the crystal. The pump-beam of thislaser is collimated with a collimating lens 44, and transmitted to theprimary laser rod through the high reflectance infrared mirror 45. Thishigh reflectance mirror allows the diode pump laser beam to betransmitted, while reflecting infrared light from the primary laser.

The Er:YAG lasing material is the preferred material for the laser rodbecause the wavelength of the electromagnetic energy emitted by thislaser, 2.94 microns, is very near one of the peak absorption wavelengths(approximately 3 microns) of water. Thus, this wavelength is stronglyabsorbed by water and tissue. The rapid heating of water and tissuecauses perforation or alteration of the skin.

Other useful lasing material is any material which, when induced tolase, emits a wavelength that is strongly absorbed by tissue, such asthrough absorption by water, nucleic acids, proteins or lipids, andconsequently causes the required perforation or alteration of the skin(although strong absorption is not required). A laser can effectivelycut or alter tissue to create the desired perforations or alterationswhere tissue exhibits an absorption coefficient of 10-10,000 cm⁻¹.Examples of useful lasing elements are pulsed CO₂ lasers, Ho:YAG(holmium:YAG), Er:YAP, Er/Cr:YSGG (erbium/chromium: yttrium, scandium,gallium, garnet; 2.796 microns), Ho:YSGG (holmium: YSGG; 2.088 microns),Er:GGSG (erbium: gadolinium, gallium, scandium, garnet), Er:YLF (erbium:yttrium, lithium, fluoride; 2.8 microns), Tm:YAG (thulium: YAG; 2.01microns), Ho:YAG (holmium: YAG; 2.127 microns); Ho/Nd:YA1O₃(holmium/neodymium: yttrium, alurninate; 2.85-2.92 microns), cobalt:MgF₂(cobalt: magnesium fluoride; 1.75-2.5 microns), HF chemical (hydrogenfluoride; 2.6-3 microns), DF chemical (deuterium fluoride; 3.6-4microns), carbon monoxide (5-6 microns), deep UV lasers, and frequencytripled Nd:YAG (neodymium:YAG, where the laser beam is passed throughcrystals which cause the frequency to be tripled).

Utilizing current technology, some of these laser materials provide theadded benefit of small size, allowing the laser to be small andportable. For example, in addition to Er:YAG, Ho:YAG lasers also providethis advantage.

Solid state lasers, including but not limited to those listed above, mayemploy a polished barrel crystal rod. The rod surface may also contain amatte finish as shown in FIG. 13. However, both of these configurationscan result in halo rays that surround the central output beam.Furthermore, an all-matte finish, although capable of diminishing halorays relative to a polished rod, will cause a relatively large decreasein the overall laser energy output. In order to reduce halo rays andotherwise affect beam mode, the matte finish can be present on bands ofvarious lengths along the rod, each band extending around the entirecircumference of the rod. Alternatively, the matte finish may be presentin bands along only part of the rod's circumference. FIG. 14 shows alaser crystal element in which the matte finish is present upon the fullcircumference of the element along two-thirds of its length.Alternatively, as shown in FIG. 15, matte stripes may be presentlongitudinally along the full length of the rod. The longitudinalstripes may alternatively exist along only part of the length of therod, such as in stripes of various lengths. A combination of theforegoing techniques may be used to affect beam shape. Other variationsof patterns may also be employed in light of the beam shape desired. Thespecific pattern may be determined based on the starting configurationof the beam from a 100% polished element in light of the desired finalbeam shape and energy level. A complete matte finish element may also beused as the starting reference point.

For purposes of beam shape control, any surface finish of greater than30 microinches is considered matte. A microinch equals one millionth(0.000001) inch, which is a common unit of measurement employed inestablishing standard roughness unit values. The degree of roughness iscalculated using the root-mean-square average of the distances inmicroinches above or below the mean reference line, by taking the squareroot of the mean of the sum of the squares of these distances. Althoughmatte surfaces of greater than 500 microinches may be used to affectbeam shape, such a finish will seriously reduce the amount of lightenergy that enters the crystal rod, thereby reducing the laser's energy.

To remove the beam halo, a matte area of approximately 50 microinches ispresent around the full circumference of an Er:YAG laser rod fortwo-thirds the length of the rod. The non-matte areas of the rod areless than 10 microinches. A baseline test of the non-matte rod can befirst conducted to determine the baseline beam shape and energy of therod. The matte areas are then obtained by roughing the polished crystallaser rod, such as with a diamond hone or grit blaster. The specificpattern of matte can be determined with respect to the desired beamshape and required beam energy level. This results in a greatly reducedbeam halo. The rod may also be developed by core drilling a boule ofcrystal so that it leaves an overall matte finish and then polishing thedesired areas, or by refining a partially matte, partially polishedboule to achieve the desired pattern.

The beam shape of a crystal laser rod element may alternatively bemodified as in FIG. 16 by surrounding the rod 20 in a material 160 whichis transparent to the exciting light but has an index of refractiongreater than the rod. Such a modification can reduce the halo of thebeam by increasing the escape probability of off-axis photons within thecrystal. This procedure may be used in place of or in addition to theforegoing matte procedure.

The emitted laser beam is focused down to a millimeter or submillimetersized spot with the use of the focusing lens 28. Consideration of lasersafety issues suggests that a short focal length focusing lens be usedto ensure that the energy fluence rate (W/cm²) is low except at thefocus of the lens where the tissue sample to be perforated or altered ispositioned. Consequently, the hazard of the laser beam is minimized.

The beam can be focused so that it is narrower along one axis than theother in order to produce a slit-shaped perforation or alterationthrough the use of a cylindrical focusing lens 27. This lens, whichfocuses the beam along one axis, is placed in series with thetransmitting focusing lens 28. When perforations or alterations areslit-shaped, the patient discomfort or pain associated with theperforation or alteration is considerably reduced.

Optionally, the beam can be broadened, for instance through the use of aconcave diverging lens 46 (FIG. 4) prior to focusing through thefocusing lens 28. This broadening of the beam results in a laser beamwith an even lower energy fluence rate a short distance beyond the focalpoint, consequently reducing the hazard level. Furthermore, this opticalarrangement reduces the optical aberrations in the laser spot at thetreatment position, consequently resulting in a more precise perforationor alteration.

Also optionally, the beam can be split by means of a beam-splitter tocreate multiple beams capable of perforating or altering several sitessimultaneously or near simultaneously. FIG. 5 provides two variations ofuseful beam splitters. In one version, multiple beam splitters 48 suchas partially silvered mirrors, dichroic mirrors, or beam-splittingprisms can be provided after the beam is focused. Alternatively, anacousto-optic modulator 52 can be supplied with modulated high voltageto drive the modulator 52 and bend the beam. This modulator is outsidethe laser cavity. It functions by deflecting the laser beam sequentiallyand rapidly at a variety of angles to simulate the production ofmultiple beams.

Portability

Currently, using a portable TRANSMEDICA™ Er:YAG laser, the unitdischarges once per 20-30 seconds. This can be increased by adding abattery and capacitor and cooling system to obtain a quicker cycle.Multiple capacitors can be strung together to get the discharge ratedown to once every 5 or 10 seconds (sequentially charging the capacitorbanks). Thus, getting a higher repetition rate than with a singlecapacitor.

The TRANSMEDICA™ Er:YAG laser incorporates a flashlamp, the output ofwhich is initiated by a high-voltage pulse of electricity produced by acharged capacitor bank. Due to the high voltages required to excite theflashlamp, and because the referred to version of the laser incorporatesdry cells to run (thus the charging current is much less than awall-plug could provide), then the capacitors take about 20 seconds tosufficiently charge. Thus, if a pulse repetition rate of 1 pulse/20seconds is desirable, it would be suitable to have multiple capacitorbanks that charge sequentially (i.e. as one bank fires the flashlamp,another bank, which has been recharging, fires, and so on). Thus, thepulse repetition rate is limited only be the number of capacitor banksincorporated into the device (and is also limited by the efficiency ofwaste-heat removal from the laser cavity).

A small heater, such as a thermoelectric heater 32, is optionallypositioned at the end of the laser applicator proximal to the site ofperforation. The heater raises the temperature of the tissue to beperforated or altered prior to laser irradiation. This increases thevolume of fluid collected when the device is used for that purpose. Asuggested range for skin temperature is between 36 EC and 45 EC,although any temperature which causes vasodilation and the resultingincrease in blood flow without altering the blood chemistry isappropriate.

Container Unit

A container unit 68 is optionally fitted into the laser housing and ispositioned proximal to the perforation or alteration site. The containerunit reduces the intensity of the sound produced when the laser beamperforates or alters the patient's tissue, increases the efficiency offluid, gas or other biomolecule collection, and collects the ablatedtissue and other matter released by the perforation. The container unitcan be shaped so as to allow easy insertion into the laser housing andto provide a friction fit within the laser housing. FIG. 8 shows atypical container unit inserted into the laser housing and placed overthe perforation site.

The container unit 68 comprises a main receptacle 82, including a lens84. The main receptacle collects the fluid, gas or other biomoleculesample, the ablated tissue, and/or other matter released by theperforation. The lens is placed such that the laser beam may passthrough the lens to the perforation site but so that the matter releasedby the perforation does not splatter back onto the applicator. Thecontainer unit also optionally includes a base 86, attached to thereceptacle. The base can optionally be formed so as to be capable ofbeing inserted into the applicator to disengage a safety mechanism ofthe laser, thereby allowing the laser beam to be emitted.

As shown in FIGS. 17a through 17 g, the shape and size of the containerunit 68 are such as to allow placement next to or insertion into theapplicator, and to allow collection of the fluid, gas or otherbiomolecule samples, ablated tissue, and/or other matter released by theperforation or alteration. Examples of shapes that the main receptaclemay take include cylinders, bullet shapes, cones, polygons and free formshapes. Preferably, the container unit has a main receptacle, with avolume of around 1-2 milliliters. However, larger and smallerreceptacles will also function appropriately.

The lens 84, which allows the laser beam to pass through whilepreventing biological and other matter from splattering back onto theapplicator, is at least partially transparent. The lens is constructedof a material that transmits the laser wavelength utilized and ispositioned in the pathway of the laser beam, at the end of the containerunit proximal to the beam. The transmitting material can be quartz, butother examples of suitable infrared transmitting materials include rocksalt, germanium, glass, crystalline sapphire, polyvinyl chloride andpolyethylene. However, these materials should not contain impuritiesthat absorb the laser beam energy. As shown in FIG. 20, the lens mayoptionally include a mask of non-transmitting material 85 such that thelens may shape the portion of the beam that is transmitted to theperforation site.

The main receptacle 82 is formed by the lens and a wall 88, preferablyextending essentially away from the perimeter of the lens. The open endof the main receptacle or rim 90 is placed adjacent to the perforationor alteration site. The area defined by the lens, wall of the mainreceptacle and perforation or alteration site is thereby substantiallyenclosed during the operation of the laser.

The base 86 is the part of the container unit that can optionally beinserted into the applicator. The base may comprise a cylinder, aplurality of prongs or other structure. The base may optionally havethreading. Optionally, the base, when fully inserted, disengages asafety mechanism of the laser, allowing the emission of the laser beam.

A typical container unit can comprise a cylindrical main receptacle 82,a cylindrical base 86, and an at least partially transparent circularlens 84 in the area between the main receptacle and base. Optionally,the lens may include a mask that shapes the beam that perforates thetissue. The interior of the main receptacle is optionally coated withanticoagulating and/or preservative chemicals. The container unit can beconstructed of glass or plastic. The container unit is optionallydisposable.

FIG. 19 shows examples of the use of a container unit with a laser forthe purpose of drawing fluids, gases or other biomolecules or toadminister pharmaceuticals. In this embodiment the applicator 30 issurrounded by the housing 34. The container unit is inserted in theapplicator 30 and aligned so as to be capable of defeating the interlock36. The base 86 of the container unit in this embodiment is within theapplicator 30, while the rim 90 of the receptacle 82 is located adjacentto the tissue to be perforated.

Additionally, the container unit can be evacuated. The optional vacuumin the container unit exerts a less than interstitial fluid or thepressure of gases in the blood over the perforation or alteration site,thereby increasing the efficiency in fluid, gas or other biomoleculecollection. The container unit is optionally coated with anticoagulatingand/or preservative chemicals. The container unit's end proximal to theperforation or alteration site is optionally sealed air-tight with aplug 70. The plug is constructed of material of suitable flexibility toconform to the contours of the perforation site (e.g., the finger). Thedesired perforation or alteration site is firmly pressed against theplug. The plug's material is preferably impermeable to gas transfer.Furthermore, the plug's material is thin enough to permit perforation ofthe material as well as perforation of the skin by the laser. The plugcan be constructed of rubber, for example.

The plug perforation center 74, as shown in FIG. 9, is preferablyconstructed of a thin rubber material. The thickness of the plug is suchthat the plug can maintain the vacuum prior to perforation, and thelaser can perforate both the plug and the tissue adjacent to the plug.For use with an Er:YAG laser, the plug can be in the range ofapproximately about 100 to 500 microns thick.

The plug perforation center 74 is large enough to cover the perforationor alteration site. Optionally, the perforated site is a round hole withan approximate diameter ranging from about 0.1-1 mm, or slit shaped withan approximate width of about 0.05-0.5 mm and an approximate length upto about 2.5 mm. Thus, the plug perforation center is sufficiently largeto cover perforation sites of these sizes.

As shown in FIG. 10, the container unit 68 can include a hole 76 throughwhich the laser passes. In this example, the container unit optionallysolely collects ablated tissue. As in the other examples, the site ofirradiation is firmly pressed against the container unit. The containerunit can optionally include a plug proximal to the perforation site,however it is not essential because there is no need to maintain avacuum. The container unit reduces the noise created from interactionbetween the laser beam and the patient's tissue and thus alleviates thepatient's anxiety and stress.

The container may also be modified to hold, or receive through anopening, a pharmaceutical or other substance, which may then bedelivered simultaneously, or shortly after irradiation occurs. FIG. 11shows an example of a container with a built-in drug reservoir androll-on apparatus for delivery. FIG. 18 shows a container with anapplicator which in turn comprises an atomizer with attached highpressure gas cylinder.

Optionally, the container unit is disposable, so that the container unitand plug can be discarded after use.

In order to sterilize the skin before perforation or alteration, asterile alcohol-impregnated patch of paper or other thin material canoptionally be placed over the site to be perforated. This material canalso prevent the blowing off of potentially infected tissue in the plumereleased by the perforation. The material must have low bulk absorptioncharacteristics for the wavelength of the laser beam. Examples of suchmaterial include, but are not limited to, a thin layer of glass, quartz,mica, or sapphire. Alternatively, a thin layer of plastic, such as afilm of polyvinyl chloride or polyethylene, can be placed over the skin.Although the laser beam may perforate the plastic, the plastic preventsmost of the plume from flying out and thus decreases any potential riskof contamination from infected tissue. Additionally, a layer of aviscous sterile substance such as vaseline can be added to thetransparent material or plastic film to increase adherence of thematerial or plastic to the skin and further decrease plumecontamination. Additionally, such a patch can be used to deliverallergens, local anesthetics or other pharmaceuticals as describedbelow.

Examples of such a patch are provided in FIGS. 6 and 7. In FIG. 6,alcohol impregnated paper 54 is surrounded by a temporary adhesive strip58. Side views of two alternative patches are shown in FIG. 7, where asterilizing alcohol, antibiotic ointment, allergen, or pharmaceutical ispresent in the central region of the patch 60. This material is held inplace by a paper or plastic layer 62, optionally with alaser-transparent material 64. Examples of such material include, butare not limited to, mica, quartz or sapphire which is transparent to thelaser beam at the center of the patch. However, the material need not betotally transparent. The patch can be placed on the skin using anadhesive 66.

Modulated Laser

In addition to the pulsed lasers listed above, a modulated laser can beused to duplicate a pulsed laser for the purpose of enhancing topicaldrug delivery, as well as enhancing the removal of fluids, gases orother biomolecules. This is accomplished by chopping the output of thecontinuous-wave laser by either modulating the laser outputmechanically, optically or by other means such as a saturable absorber.(See, e.g., Jeff Hecht, “The Laser Guidebook,” McGraw-Hill:NY, 1992).Examples of continuous-wave lasers include CO₂ which lases over a rangebetween 9-11 microns (e.g. Edinburgh Instruments, Edinburgh, UK),Nd:YAG, Thullium:YAG (Tm:YAG), which lases at 2.1 microns (e.g. CLRPhotonics Inc., Boulder Colo.), semiconductor (diode) lasers which laseover a range from 1.0-2.0 microns (SDL Inc., San Jose, Calif.).

The chopping of the laser output (for example, with a mechanical chopperfrom Stanford Research Instruments Inc., Sunnyvale Calif.) willpreferably result in discrete moments of irradiation with temporalwidths from a few tenths of milliseconds, down to nanoseconds orpicoseconds. Alternatively, in the case of diode lasers, the lasingprocess can be modulated by modulating the laser excitation current. Amodulator for a laser diode power supply can be purchased from SDL Inc.,San Jose, Calif. Alternatively, the continuous-wave beam can beoptically modulated using, for example, an electro-optic cell (e.g. fromNew Focus Inc., Santa Clara, Calif.) or with a scanning mirror fromGeneral Scanning, Inc., Watertown Mass.

The additive effect of multiple perforations may be exploited with diodelasers. Laser diodes supplied by SDL Corporation (San Jose, Calif.)transmit a continuous beam of from 1.8 to 1.96 micron wavelength radiantenergy. These diodes operate at up to 500 mW output power and may becoupled to cumulatively produce higher energies useful for stratumcorneum ablation. For example, one diode bar may contain ten such diodescoupled to produce pulsed energy of 5 mJ per millisecond. It has beenshown that an ablative effect may be seen with as little as 25 mJ ofenergy delivered to a 1 mm diameter spot. Five 5 millisecond pulses or(25) one millisecond pulses from a diode laser of this type will thushave an ablative effect approximately equivalent to one 25 mJ pulse inthe same time period.

The following examples are descriptions of the use of a laser toincrease the permeability of the stratum corneum for the purpose ofdrawing fluids, gases or other biomolecules, as well as forpharmaceutical delivery. These examples are not meant to limit the scopeof the invention, but are merely embodiments.

EXAMPLE 1

The laser comprises a flashlamp (PSC Lamps, Webster, N.Y.), an Er:YAGcrystal (Union Carbide Crystal Products, Washagoul, Wash.),optical-resonator mirrors (CVI Laser Corp., Albuquerque, N. Mex.), aninfrared transmitting lens (Esco Products Inc., Oak Ridge, N.J.), aswell as numerous standard electrical components such as capacitors,resistors, inductors, transistors, diodes, silicon-controlledrectifiers, fuses and switches, which can be purchased from anyelectrical component supply firm, such as Newark Electronics, LittleRock, Ark.

EXAMPLE 2

An infrared laser radiation pulse was formed using a solid state,pulsed, Er:YAG laser consisting of two flat resonator mirrors, an Er:YAGcrystal as an active medium, a power supply, and a means of focusing thelaser beam. The wavelength of the laser beam was 2.94 microns. Singlepulses were used.

The operating parameters were as follows: The energy per pulse was 40,80 or 120 mJ, with the size of the beam at the focal point being 2 mm,creating an energy fluence of 1.27,2.55 or 3.82 J/cm². The pulsetemporal width was 300 μs, creating an energy fluence rate of 0.42, 0.85or 1.27×10⁴ W/cm².

Transepidermal water loss (TEWL) measurements were taken of the volaraspect of the forearms of human volunteers. Subsequently the forearmswere positioned at the focal point of the laser, and the laser wasdischarged. Subsequent TEWL measurements were collected from theirradiation sites, and from these the measurements of unirradiatedcontrols were subtracted. The results (shown in FIG. 27) show that atpulse energies of 40, 80 and 120 mJ, the barrier function of the stratumcorneum was reduced and the resulting water loss was measured to be 131,892 and 1743 gm/m²/hr respectively. The tape stripe positive control (25pieces of Scotch Transpore tape serially applied and quickly removedfrom a patch of skin) was measured to be 9.0 gm/m²/hr, greater thanuntouched controls; thus the laser is more efficient at reducing thebarrier function of the stratum corneum than tape-stripping.

Clinical assessment was conducted 24 hours after irradiation. Only asmall eschar was apparent on the site lased at high energy, and no edemawas present. None of the volunteers experienced irritation or requiredmedical treatment.

EXAMPLE 3

An infrared laser radiation pulse was formed using a solid state,pulsed, Er:YAG laser consisting of two flat resonator mirrors, an Er:YAGcrystal as an active medium, a power supply, and a means of focusing thelaser beam. The wavelength of the laser beam was 2.94 microns. A singlepulse was used.

The operating parameters were as follows: The energy per pulse was 60mJ, with the size of the beam at the focal point being 2 mm, creating anenergy fluence of 1.91 J/cm². The pulse temporal width was 300 μs,creating an energy fluence rate of 0.64×10⁴ W/cm².

The volar aspect of the forearm of a volunteer was placed at the focalpoint of the laser, and the laser was discharged. After discharge of thelaser, the ablated site was topically administered a 30% liquidlidocaine solution for two minutes. A 26G-0.5 needle was subsequentlyinserted into the laser ablated site with no observable pain.Additionally, after a 6-minute anesthetic treatment, a 22G-1 needle wasfully inserted into the laser ablated site with no observable pain. Thevolunteer experienced no irritation and did not require medicaltreatment.

EXAMPLE 4

Ablation threshold energy: Normally hydrated (66%) stratum corneum wassandwiched between two microscope cover slides, and exposed to a singlepulse of irradiation from the Er:YAG laser. Evidence of ablation wasdetermined by holding the sample up to a light and seeing whether anystratum corneum was left at the irradiated site. From this experiment,it was determined that the irradiation threshold energy (for a 2 mmirradiation spot) was approximately 90-120 mJ. The threshold will likelybe higher when the stratum corneum is still overlying epidermis, as innormal skin, since it takes energy to remove the stratum corneum fromthe epidermis, to which it is adherent.

EXAMPLE 5

Differential Scanning Calorimetry (DSC): FIG. 28 shows a DSC scan ofnormally hydrated (66%) human stratum corneum, and a scan of stratumcorneum irradiated with the Er:YAG laser using a subablative pulseenergy of 60 mJ. Defining the thermal transition peaks at approximately65, 80 and 92° C., we determined the heat of transition (μJ), center ofthe transition (° C.) and the full-width at half-maximum of thetransition (° C.) (FIGS. 29-31). The results shown are on normal 66%hydrated stratum corneum, dehydrated 33% stratum corneum, steam heatedstratum corneum, Er:YAG laser irradiated stratum corneum, or stratumcorneum that was immersed in chloroform-methanol (a lipid solvent), orbeta-mercaptoethanol (a protein denaturant). The effect of laserirradiation on stratum corneum is consistent (depending on whichtransition you look at, 1, 2 or 3) with changes seen due to thermaldamage (i.e. heated with steam), and delipidization. Permeation with(³H₂O) and transepidermal impedance experiments on skin treated the sameway showed that the result of these treatments (heat, solvent ordenaturant) resulted in increased permeation. Thus, the changes inducedin the stratum corneum with these treatments, changes which areconsistent with those seen in laser irradiated stratum corneum, andchanges which do not result in stratum corneum ablation, result inincreased permeation.

EXAMPLE 6

Fourier Transform Infrared (FTIR) Spectroscopy: FTIR spectroscopy wasused to study stratum corneum treated the same way as in the above DSCexperiments, except the energy used was between 53 and 76 mJ. Thespectra (see, e.g., FIGS. 32-33) show that absorption bands that are dueto water, proteins and lipids change when the stratum corneum isirradiated. Some of these changes are consistent with changes seenduring non-laser treatment of the stratum corneum (e.g. desiccation,thermal damage, lipid solubilization or protein denaturation). Forexample, the Amide I and II bands, which are due to the presence ofproteins (most likely keratin, which makes up the bulk of protein instratum corneum), shift to a larger wavenumber, consistent with theeffect of desiccation alone (in the case of Amide II) or desiccation andbeta-mercaptoethanol treatment (in the case of Amide I) (see, e.g., FIG.34). The CH₂, vibrations (due to bonds in lipids) always shift to asmaller wavenumber indicating that either the intermolecular associationbetween adjacent lipid molecules has been disturbed and/or theenvironment around the lipid molecules has changed in such a way thatthe vibrational behavior of the molecules changes (see, e.g., FIG. 35).

EXAMPLE 7

Histology: Numerous in vivo experiments have been done on rats andhumans. Usually, the skin is irradiated with the Er:YAG laser and a 2 mmspot and with a particular pulse energy, and then the irradiated site isbiopsied immediately or 24 hours later. Two examples of typical resultsare shown in FIGS. 36 and 37. FIG. 36 shows rat skin irradiated at 80mJ, which is an energy sufficient to make the skin permeable (tolidocaine, for instance) and yet does not show any sign of stratumcorneum ablation. FIG. 37 depicts human skin 24 hours after beingirradiated at 80 mJ. In this case, some change in the appearance of thestratum corneum has taken place (perhaps coagulation of some layers ofstratum corneum into a darkly staining single layer), and yet thestratum corneum is still largely intact and is not ablated. Irradiationof human skin, in vivo, and subsequently examined under a dissectionmicroscope, show that at subablative energies (less than about 90-120mJ), the stratum corneum is still present on the skin. The irradiatedstratum corneum appears slightly whitened in vivo, which might beevidence of desiccation or separation of the stratum corneum from theunderlying tissues.

EXAMPLE 8

One way to quantify the reduction in the barrier function of the stratumcorneum is to measure the reduction in the electrical impedance of theskin as a consequence of laser irradiation. In this experiment, separate2 mm spots on the volar aspect of the forearm of a human volunteer wereirradiated with a single pulse of radiant energy from the Er:YAG laserusing a range of energies. An ECG electrode was then placed over theirradiated site and an unirradiated site about 20 cm away on the sameforearm. A 100 Hz sine wave of magnitude 1 volt peak-to-peak was thenused to measure the impedance of the skin. The results of a series ofmeasurements are shown in FIG. 22, which shows that there is a decreasein skin impedance in skin irradiated at energies as low as 10 mJ, usingthe fitted curve to interpolate data.

EXAMPLE 9

Pieces of human skin were placed in diffusion cells and irradiated witha single pulse of radiant energy produced by an Er:YAG laser. The spotsize was 2 mm and the energy of the pulse was measured with a calibratedenergy meter. After irradiation, the diffusion cells were placed in a 37degrees Celsius heating block. Phosphate buffered saline was added tothe receptor chamber below the skin and a small stir bar was inserted inthe receptor chamber to keep the fluid continually mixed. Control skinwas left unirradiated. Small volumes of radiolabelled compounds (eithercorticosterone or DNA) were then added to the donor chamber and left for15 minutes before being removed (in the case of corticosterone) or wereleft for the entire duration of the experiment (in the case of the DNA).Samples were then taken from the receptor chamber at various times afterapplication of the test compound and measured in a scintillation orgamma counter. The results of this experiment are shown in FIGS. 21 and26. The results illustrate that enhanced permeation can occur atsub-ablative laser pulse energies (see the 77 mJ/pulse data forcorticosterone). Although, in the case of the DNA experiment the energyused may have been ablative, enhanced permeation may still occur whenlower energies are used.

EXAMPLE 10

Histology studies on rat and human skin, irradiated either in vivo or invitro, show little or no evidence of ablation when Er:YAG laser pulseenergies less than about 100-200 mJ are used. (See, e.g., FIGS. 25a and25 b). Repeating this study showed the same results as the previousstudies. An in vitro permeation study using tritiated water (³H₂O)involving human skin lased at energies from 50 mJ (1.6 J/cm²) to 1250 mJ(40 J/cm²) determined (FIGS. 23 and 24) than an increase in permeationwas seen at low energy fluences up to about 5 J/cm², whereupon thepermeation is more-or-less constant. This shows that there has been alased induced enhancement of permeation (of tritiated water) at energiesthat are sub-ablative.

EXAMPLE 11

The output of the Er:YAG laser was passed through an aperture to defineit's diameter as 2 mm. Human skin, purchased from a skin bank, waspositioned in Franz diffusion cells. The receptor chamber of the cellwas filled with 0.9% buffered saline. A single pulse, of measuredenergy, was used to irradiate the skin in separate diffusion cells.Control skin was left unirradiated. When the permeation of lidocaine wasto be tested, a 254 mJ pulse was used, and multiple samples wereirradiated. In the case of γ-interferon, a 285 mJ pulse was used, andmultiple samples were irradiated. In the case of insulin, a 274 mJ pulsewas used, and multiple samples were irradiated. In the case ofcortisone, either 77 mJ or 117 mJ was used. After irradiation, astirring magnet was place in the receptor chamber of the diffusion cellsand the cells were placed in a heating block held at 37° C. Theradiolabelled lidocaine, gamma-interferon and insulin were diluted inbuffered saline, and 100 μL of the resulting solutions was placed in thedonor chamber of separate diffusion cells. The donor was left on theskin for the duration of the experiment. At various timespost-drug-application, samples were taken from the receptor chamber andthe amount of drug present was assayed with either a gamma-counter, or aliquid scintillation counter. Graphs of the resulting data are shown inFIGS. 39, 40 and 41. From this, and similar data, the permeabilityconstants were derived and are shown as follows:

Drug Permeability Constant, k_(p) (× 10⁻³ cm/hr) Lidocaine 2.62 +/− 6.9 γ-Interferon 9.74 +/− 2.05 Insulin 11.3 +/− 0.93

EXAMPLE 12

This data was collected during the same experiment as the TEWL results(see Example 2 and FIG. 27). In the case of the blanching assay,baseline skin color (redness) measurements were then taken of each spotusing a Minolta CR-300 Chromameter (Minolta Inc., NJ). The Er:YAG laserwas then used to ablate six 2 mm spots on one forearm, at energies of40, 80 and 120 mJ. A spot (negative calorimeter control) directlyadjacent to the laser irradiated spots remained untouched. Subsequently,a thin film of 1% hydrocortisone ointment was applied to six of thelased spots on the treatment arm. One untouched spot on thecontralateral arm was administered a thin layer of Diprolene(β-methasone), which is a strong steroid that can permeate the intactstratum corneum in an amount sufficient to cause measurable skinblanching. An occlusive patch, consisting of simple plastic wrap, wasfixed with gauze and dermatological tape over all sites on both arms andleft in place for two hours, after which the administered steroids weregently removed with cotton swabs. Colorimeter measurements were thentaken over every unirradiated and irradiated spot at 2, 4, 8, 10, 12 and26 hours post-irradiation, these results are shown in FIGS. 38a and 38b. Finally, the skin was clinically assessed for evidence of irritationat the 26 hour evaluation.

The results of the chromameter measurements show that some erythema(reddening) of the skin occurred, but because of the opposite-actingblanching permeating hydrocortisone, the reddening was less than thatseen in the control spots which did not receive hydrocortisone. TheDiprolene control proved the validity of the measurements and noproblems were seen in the volunteers at the 26 hour evaluation, althoughin some of the cases the site of irradiation was apparent as a small redspot.

EXAMPLE 13

The radiant output of the Er:YAG laser is focussed and collimated withoptics to produce a spot size at the surface of the skin of, forexample, 5 mm. The skin of the patient, being the site of, or close tothe site of disease, is visually examined for anything that might affectthe pharmacokinetics of the soon to be administered drug (e.g.,significant erythema or a wide-spread loss of the integrity of thestratum corneum). This site, which is to be the site of irradiation, isgently cleansed to remove all debris and any extraneous compounds suchas perfume or a buildup of body oils. A disposable tip attached to thelaser pressed up to the skin prior to irradiation is used to contain anyablated biological debris, as well as to contain any errant radiantenergy produced by the laser. A single laser pulse (approximately 350 μslong), with an energy of 950 mJ, is used to irradiate the spot. Theresult is a reduction or elimination of the barrier function of thestratum corneum. Subsequently, an amount of pharmaceutical,hydrocortisone for example, is spread over the irradiation site. Thepharmaceutical may be in the form of an ointment so that it remains onthe site of irradiation. Optionally, an occlusive patch is placed overthe drug in order to keep it in place over the irradiation site.

EXAMPLE 14

An infrared laser radiation pulse was formed using a solid state,pulsed, Er:YAG laser consisting of two flat resonator mirrors, an Er:YAGcrystal as an active medium, a power supply, and a means of focusing thelaser beam. The wavelength of the laser beam was 2.94 microns. Theduration of the pulse was approximately 300 μs. The spot size wasapproximately 2 mm, with an energy fluence of 5 J/cm². Single pulseswere used.

Three 2 mm diameter spots were created on a flaccid penis. Subsequent toablation a pharmaceutical preparation of alprostadil (Caverject fromPharmacia & Upjohn, Kalamazoo, Mich.) was applied to a small patchconsisting of tissue paper. The patch was applied to the multipleperforated areas of the skin on the then flaccid penis and held therewith adhesive tape for 45 minutes. After approximately 35 minutes, thepatient obtained an erection that was sustained for more than 1 hour.

The benefit of this route of administration is that it is painless. Thenormal method of administration of alprostadil involves injecting thecompound deep into the corpus cavernosum of the penis with a hypodermicneedle. Not only is such a procedure painful, but it also results inpotentially infectious contaminated sharp.

EXAMPLE 15

An infrared laser radiation pulse can be formed using a solid state,pulsed, Er:YAG laser consisting of two flat resonator mirrors, an Er:YAGcrystal as an active medium, a power supply, and a means of focusing thelaser beam. The wavelength of the laser beam is preferably 2.94 microns.The duration of the pulse is preferably approximately 300 μs. The spotsize is preferably approximately 2 mm, with an impulse energy ofapproximately 150 mJ creating an energy fluence of approximately 5J/cm².

Single pulses of radiant energy from the TRANSMEDICA™ Er:YAG laser, withthe operating parameters described above, is preferably used toirradiate 2 mm diameter spots on areas of the scalp exhibiting hairloss. Multiple irradiation sites can be used. Subsequent to irradiation,minoxidil (for example Rogaine from Pharmacia & Upjohn, Kalamazoo,Mich.) may be applied to access interstitial spaces in the scalp,allowing greater quantities of the pharmaceutical to stimulate rootfollicles than is available by transcutaneous absorption alone.Alternatively, subsequent to ablation, androgen inhibitors may beapplied through the laser ablated sites. These inhibitors act to counterthe effects of androgens in hair loss.

EXAMPLE 16

Skin resurfacing is a widely used and commonly requested cosmeticprocedure whereby wrinkles are removed from (generally) the face of apatient by ablating approximately the outermost 400 microns of skin withthe radiant energy produced by a laser (Dover J. S., Hruza G. J., “LaserSkin Resurfacing,” Semin. Cutan. Med. Surg., 15(3):177-88, 1996). Aftertreatment, often a “mask” made out of hydrogel (which is a gelatine-likematerial that consists mostly of water) is applied to the irradiatedarea to provide both a feeling of coolness and also to preventundesirable desiccation of the treated skin and “weeping” of bodilyfluids.

The pain associated with this procedure would be intolerable without theuse of local or general anesthesia. Generally, multiple (perhaps up to30) local injections of lidocaine are completed prior to the irradiationof the skin. These injections themselves take a significant amount oftime to perform and are themselves relatively painful.

Single pulses of radiant energy from the TRANSMEDICA™ Er:YAG laser ispreferably used to irradiate 2 mm diameter spots on areas of the facerequired for the multiple applications of lidocaine prior to skinresurfacing. The energy used in each laser pulse is preferably 150 mJ.Subsequent to irradiation, lidocaine is applied for general anesthesia.Furthermore, by incorporating lidocaine (preferably, the hydrophillicversion which is lidocaine-HCl) into the hydrogel, or other patch or gelmeans of containment, and applying this complex (in the physical form ofa “face-mask”) to the patient's face prior to the laser irradiation butafter ablating the stratum corneum with the Er:YAG laser from a matrixof sites throughout the treatment area, sufficient anesthesia will beinduced for the procedure to be done painlessly. It may also bebeneficial to incorporate a sedative within the hydrogel to furtherprepare the patient for what can be a distressing medical procedure.Optionally, the “face-mask” can be segmented into severalaesthetic-units suitable for single application to particularlaser-treatment regions of the face. Finally, another “face-mask”incorporating beneficial pharmaceuticals, such as antibiotics (e.g.Bacitracin, Neosporin, Polysporin, and Sulphadene) or long term topicalor systemic analgesics, such as fentanyl or demeral, can be applied tothe patient after skin resurfacing treatment.

EXAMPLE 17

The growth of hairs in the nose (primarily in men) is a common cosmeticproblem. The current therapy, which involves pulling the hairs out withtweezers, is painful and nonpermanent. An infrared laser radiation pulsecan be formed using a solid state, pulsed, Er:YAG laser consisting oftwo flat resonator mirrors, an Er:YAG crystal as an active medium, apower supply, and a means of focusing the laser beam. The wavelength ofthe laser beam is preferably 2.94 microns. The duration of the pulseapproximately is preferably 300 μs. The spot size is preferablyapproximately 2 mm, with an impulse energy of approximately 150 mJcreating an energy fluence of approximately 5 J/cm².

Single pulses of radiant energy from the TRANSMEDICA™ Er:YAG laser ispreferably used, with the above described operating parameters, toirradiate 2 mm diameter spots on the nasal mucosa exhibitingcosmetically unappealing hair growth. Multiple irradiation sites can beused. The irradiation by itself can be sufficient to alter the tissuethereby inhibiting subsequent hair growth thus irradiation may be itselfsufficient to alter the tissue, inhibiting subsequent hair growth.Alternatively, subsequent to irradiation, a dye, for example indocyaninegreen, which absorbs different wavelengths of radiation, can be applied.After the dye has been absorbed into the nasal passage, 810 nm radiantenergy from a diode laser (GaAlAs laser) can be used to raise thetemperature of the surrounding tissue. This acts to selectively damagethe hair follicles in contact with the dye. As a result the nasal tissueis modified so that hair growth does not reoccur, or at least does notrecur as quickly as it does after manual hair removal.

While various applications of this invention have been shown anddescribed, it should be apparent to those skilled in the art that manymodifications of the described techniques are possible without departingfrom the inventive concepts herein.

We claim:
 1. A method for altering skin permeability that does notablate the stratum corneum, comprising the steps of: a) focusing a laserbeam with sufficient energy fluence to alter the skin at least as deepas the stratum corneum, but not as deep as the capillary layer; and b)firing the laser to create a site of alteration, the site having adiameter of between 0.5 microns and 5.0 cm.
 2. The method of claim 1wherein the laser beam has a wavelength of 0.2-10 microns.
 3. The methodof claim 1 wherein the laser beam has a wavelength of between 1.5-3.0microns.
 4. The method of claim 1 wherein the laser beam has awavelength of about 2.94 microns.
 5. The method of claim 1 wherein thelaser beam is emitted by a laser selected from the group consisting ofEr:YAG, pulsed CO₂, Ho:YAG, Er:YAP, Er/Cr:YSGG, Ho:YSGG, Er:GGSG,Er:YLF, Trn:YAG, Ho:YAG, Ho/Nd:Yalo₃, cobalt:MgF₂, HF chemical, DFchemical, carbon monoxide, deep UV lasers, and frequency tripled Nd:YAGlasers.
 6. The method of claim 1 wherein the laser beam is emitted by anEr:YAG laser.
 7. The method of claim 1 wherein the laser beam is emittedby a modulated laser selected from the group consisting ofcontinuous-wave CO₂, Nd:YAG, Thullium:YAG and diode lasers.
 8. Themethod of claim 1 wherein the laser beam is focused at a site on theskin with a diameter of 0.1-5.0 mm.
 9. The method of claim 1 wherein theenergy fluence of the laser beam at the skin is 0.03-100,000 J/cm². 10.The method of claim 1 wherein the energy fluence of the laser beam atthe skin is 0.03-9.6 J/cm².
 11. The method of claim 1 wherein the pulsewidth is between 1 femtosecond and 1,000 microseconds.
 12. The method ofclaim 1 wherein the pulse width is between 1 and 1000 microseconds. 13.The method of claim 1 wherein multiple alterations are made to preparethe skin for pharmaceutical delivery.
 14. The method of claim 1 furthercomprising a beam splitter positioned to create, simultaneously from thelaser, multiple sites of alteration.
 15. The method of claim 14 whereinthe beam splitter is selected from a series of partially silveredmirrors, a series of dichroic mirrors, and a series of beam-splittingprisms.
 16. The method of claim 1 further comprising a means to deflectthe beam at different angles to create different sites of alteration onthe skin.
 17. The method of claim 1 further comprising a means to scanthe laser beam to create one continuous path of alteration.
 18. Themethod of claim 1 further comprising the step of applying atherapeutically effective amount of a pharmaceutical composition at thesite of alteration.
 19. The method of claim 18 wherein thepharmaceutical composition is a locally acting pharmaceutical.
 20. Themethod of claim 19 wherein the pharmaceutical composition is ananesthetic.
 21. The method of claim 20 wherein the pharmaceuticalcomposition is lidocaine.
 22. The method of claim 19 wherein thepharmaceutical composition is selected from the group consisting ofalprostadil, minoxidil, localized antibiotic, antiviral or antifungalagents, chemotherapy or anti-cancer agents, and protein or DNA basedbiopharmaceutical agents.
 23. The method of claim 18 wherein thepharmaceutical composition is a systemically acting compound.
 24. Themethod of claim 23 wherein the pharmaceutical composition is anantibiotic.
 25. The method of claim 24 wherein the antibiotic isselected from the group consisting of tetracycline, streptomycin, sulfadrugs, kanamycin, neomycin, penicillin, and chloramphenicol.
 26. Themethod of claim 23 wherein the pharmaceutical composition is a hormone.27. The method of claim 26 wherein the hormone is selected from thegroup consisting of parathyroid hormone, growth hormone, gonadotropins,insulin, ACTH, somatostatin, prolactin, placental lactogen, melanocytestimulating hormone, thyrotropin, parathyroid hormone, calcitonin,enkephalin, and angiotensin.
 28. The method of claim 23 wherein thepharmaceutical composition is selected from the group consisting ofsteroids, non-steroids, anti-inflammatory agents, systemic antibiotics,antiviral agents, antifungal agents, and antinauseants.
 29. The methodof claim 23 wherein the pharmaceutical composition is nitorglycerin. 30.The method of claim 18 wherein the pharmaceutical composition isselected from the group consisting of antigens, allergens, andpermeation enhancers.
 31. The method of claim 18 wherein a patchcontaining the pharmaceutical composition is placed over the site ofalteration before firing the laser.
 32. The method of claim 18 wherein apatch containing the pharmaceutical composition is placed over the siteof alteration after firing the laser.